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Saturday, March 30, 2013

Parsing through a sample of the Centerfield Limestone looking for microfossils, I was pleasantly surprised to find some small "rice grains". They didn't look like Ostracods to me because they were not round nor did they have any ornamentation to them. A quick scan through the book "Ostracods of the Middle Devonian Silica Formation" changed my mind.

These are a species called Acanthoscapa devonica. Each fossil is about 2mm long. If I did my math right, the full size image is 50x (since the fossils are shown 100mm long on my screen)

According to the book (vol 1, pg 86) They are known from the Silica Shale but have also been found in the Hungry Hollow member of the Widder Formation in Ontario as well as the Centerfield member of the Ludlowville Formation in New York. They are illustrated on plate 7 (vol 2, pg. 16-17) where there is a comment that the specimen shown is from the Hungry Hollow formation and that specimens from the Silica shale often have their ends broken off.

Sunday, March 24, 2013

My next experiment with my new screen set was with a sample of eroded Silica Shale that I'd collected from an old dump bank near Sylvania, Ohio. Since the Silica Shale is contemporaneous with the Arkona formation I should find similar fossils. I had a little bit of a harder time with this sample as I think I loaded more raw material than I should have into the screens. It took me much longer to wash out the clay and I was having to filter out plant debris but in the end I had my results.

The first screen I look at is the #35 as that is where I expect to find most of the microfossils. I did find some Ostracods as well as quite a lot of broken fossils. This is likely because the sample I washed was of previously weathered material.

But it was not long before I started finding Ostracod fossils.

This last pic I think has a Quasillites sp, Ostracod in the middle left.

Onto the #60 screen and it yeilded much of the same, albeit smaller pieces. I also noticed sand grains which is not typical for the Silica shale but is to be expected in a mixed weathered environment.

The last two screens showed nothing of interest but quartz and pyrite mineral grains. I may start to ignore these when sifting. It will depend on if I can spot anything with a real microscope as opposed to my Zorb microscope camera (which is not a microscope, just a camera capturing the view through a magnifier in a case with some focus tools).

Friday, March 22, 2013

I ran a sample of the Arkona shale through my screen set to see what I could find. I didn't look too long or closely as this was meant to be a dry run or proof of concept test.

This is the rock sample that I used. Note the Phacops fossil, you'll see more of it later.

The Arkona formation is mostly clay and readily breaks down when in contact with water. In preparation for this experiment I left the chunk of matrix in some water for 24 hours to let it completely break down.

It took about a hour to get all the screening completed, the biggest obstacle is that the water will become saturated with clay while washing and needs to be replaced. So far it has been much cleaner and easier to do all the screening outside with a bucket of clean water to occasionally rinse the screens through.

Here are the results. From the #35 screen I found at least two species of Ostracod, lots of Tentaculite pieces and bits of the Trilobite that disintegrated while the clay matrix broke down.

The #60 screen had smaller bits and pieces (as is to be expected) along with some possible Ostracods but nothing that I was able to easily pick out and ID...

A Styliolinid...

Part of a Conodont/Scolecodont....

And other stuff.

Now we are getting to the really tiny stuff. The #120 screen material looked like this:

and the #230 screen material looked like this:

I took all the above photo's with my Zorb digital microscope but that only magnifies to 20X. To see anything meaningful in the #120 and #230 screens I would need a real microscope.

So the experiment was a success and I've learned a bit about how to best screen samples of clay matrix material. My next experiment will be with eroded Silica Shale from the dump piles near Sylvania, Ohio. The step after that will be to figure out the best way to separate the tiny samples for the fossils I want, ID what I find and then store them so they don't get lost.

Wednesday, March 20, 2013

I noticed today that this will be my 500th post on the blog. That means I've been regularly posting to this blog for the last three years. Well, not a full three years since my first post was on May 22nd, 2010. This is an outlet for me to express my interest in fossils, catalog my collection and coalesce my thoughts and research into a useful medium. Here's to the next 500 posts (and many more)!

I'm not going to wallow in self congratulatory pomp and circumstance. Instead I have some new toys to help me find fossils. It's a set of 6" diameter sieves to screen soil and eroded rock for microfossils.

There are six screens plus a bottom to catch the water/leftover residue. Each screen has a mesh with a different number of spaces per inch. They start with a #5 screen (fave holes per inch)...

... and include a #10 screen...

... a #35 screen...

... a #60 screen...

... a #120 screen...

... and a #230 screen (230 holes per inch)...

Through experimentation I have found that I don't really need the first two or last two screens for what I'm after. I generally only use the #35 and #60 screens to look for Ostracod fossils. Anything that the larger spaced screens would catch would be spotted with my naked eye while anything that fell through to the smaller screens would need a legitimate microscope to view.

I did buy a stereo microscope but it only has a 10x and 30x settings with eye pieces that can alter the magnification to 20x and 60x.

It's called a dissecting microscope and is, like the name states, more often used for examining dissected animal, plant and soil samples.

I also bought a rig and adapter so that I can use my camera to take pictures of my finds.

So expect to see more microfossils show up in my blog posts in the future. Right now I am sorting through residues from the Silica Shale, Arkona Shale & Centerfield Mbr. of the Ludlowville Fm. It is a nice activity to do in the winter when you can't go outside and collect macrofossils.

About Me

I'm a 40-something, life long student of Geology living in Philadelphia. My interests include Photography, Architecture and History among other things. When not cleaning my recent finds you'll find me in my backyard Hybridizing Daylilies or working in my garden. This Blog is an outlet for me to express my interest in fossils, catalog my collection and coalesce my thoughts and research into a useful medium.